Oral delivery of therapeutically active agents is a convenient and cost effective method of delivery. The active agent can be released in the mouth or anywhere in the alimentary canal. The delivery can be in a bolus, it can be intermittent, or it can be continuous.
Osmotic dispensing devices for delivery of therapeutically active agents are well known in the art. Such devices use an expansion means to deliver an agent to an environment of use over a period of hours, days or months. The expansion means absorbs liquid, expands, and acts to drive out the beneficial agent formulation from the interior of the device in a controlled, usually constant manner. The osmotic expansion means is used to controllably, usually relatively slowly, and over a period of time, deliver the agent.
Osmotic devices have also been described for prolonged and controlled delivery of one or more active agents where an initial delay of delivery is desired. U.S. Pat. No. 5,198,229, which is incorporated herein by reference, is directed to an osmotic device for delivery of an active agent to the upper gastrointestinal tract. The dispensing device comprises concentric housings that are in slidably telescoping arrangement with each other. A first expansion means imbibes fluid when placed in the stomach environment. This expansion means expands and pushes against a partition layer that in turn pushes against an active agent formulation. The active agent is delivered to the stomach environment through a small exit port in a controlled and continuous manner. After all the active agent has been delivered, the housings separate, the buoyancy chamber is exposed to the stomach environment, the density of the device increases, and the device sinks and exits out of the stomach.
U.S. Pat. No. 5,312,388, which is incorporated herein by reference, describes the use of slidably telescopic concentric housings in an osmotic device where delivery of more than one active agent is desired or where separate dosings of one active agent is desired. In a particular embodiment, initial rapid delivery of a particular active agent is followed by delayed delivery of the active agent. A loading dose of the active agent is dispensed as soon as the device enters the environment of use. Prolonged delivery is accomplished as a result of an expansion means that imbibes fluid and expands to separate the concentric housings. Upon separation, the active agent contained within the housings is dispensed.
U.S. Pat. No. 5,312,390, which is incorporated herein by reference, describes an osmotic device useful for the initially delayed delivery of an active agent. Slidably telescoping concentric housings separate following absorption of fluid through the housing. A fluid passage means is exposed to the fluid environment and the active agent is expelled in a controlled and continuous manner through an exit port at the end of the housing opposite the fluid passage means.
U.S. Pat. No. 5,358,502, which is incorporated herein by reference, describes an osmotic device with a semipermeable membrane with an agent that is pH sensitive and thus will dissolve at a given pH, thereby releasing the contents of the device.
Bolus delivery of an active agent is described in U.S. patent application Ser. No. 08/459,387, which is incorporated herein by reference. The patent application describes a fluid-imbibing drug delivery device that is useful for the delayed delivery of drug. A first and second housing are in reversibly sliding telescoping arrangement. The first housing contains an active agent and a first expansion agent. The second housing contains a second expansion agent. The second expansion agent imbibes fluid and pushes apart the housings. The drug is delivered and the first expansion agent imbibes fluid and expands to push any remaining drug out of the device.
As can be observed in the above-referenced patents and patent applications, osmotic devices have been described that provide for an initial pulse of an active agent, that provide for prolonged delivery of an active agent, and that provide for delivery of more than one active agent. However, there remains a continuing need for improved methods and systems for delivering one or more active agents in a reliable and reproducible manner.